WASTEWATER SURVEILLANCE OF SHIGA TOXIN-PRODUCING ESCHERICHIA COLI AND SHIGA TOXIN SUBTYPES IN OKLAHOMA CITY, OKLAHOMA DURING SUMMERS OF 2021 TO 2023

Abstract

Escherichia coli is one of the first human gut colonizers acquired after birth, and a fundamental participant in the human microflora. However, there are different pathogenic forms of E. coli that can produce intestinal diseases. Shiga toxin-producing E. coli (STEC) is a pathogenic variant that has been shown to damage intestinal epithelial, induce bloody diarrhea in hosts, and can progress to kidney failure, an often lethal condition known as Hemolytic Uremic Syndrome (HUS). A key distinction between STEC and other forms of pathogenic E. coli involves the presence of the Shiga toxin (stx) component, an AB toxin that inhibits protein synthesis in gastric/renal tissue and may lead to fatal organ damage. Being a gastrointestinal pathogen shed in human stool; it is a prime target for wastewater-based epidemiology. In this study, we collected influent composite wastewater samples from four wastewater treatment plants in the Oklahoma City (OKC) region at least once a week for the summers of 2021, 2022 and 2023, and developed biomolecular assays to quantify four genes that are closely related to STEC pathogenicity: eae, tir, stx1,and stx2. A total of 29 stx1 and 31 stx2 wastewater samples were successfully sequenced for stx targeted Illumina sequencing, where the relative abundance of toxin subtypes was analyzed and compared to clinical reports in OKC as well as summer trends reported by the CDC. Results revealed consistent presence of all four targets in wastewater. The intimin receptor gene tir was consistently higher in concentration than the intimin gene eae but the concentrations were correlated as expected given the cooccurrence of these genes in the LEE pathogenicity island. Illumina sequencing indicates a high variety of stx subtypes in the OKC area for both types of the toxin. Thus, this study presents evidence of persistent STEC in the OKC population, counter to reported cases, and that not just one STEC subtype is continuously circulating in the population, but instead different STEC subtypes fluctuate in the population over time.